Archer is a Fighter archetype. It's actually worse at archery than non-archetyped Fighter for the simple reason it replaces Weapon Training with a functionally identical ability that isn't Weapon Training, so it can't use Gloves of Dueling to boost its archery damage (which is actually really useful for archery).
An archetype that any character can grab so long as they intend to keep using bows and crossbows. After all, why should the fighter be the only master of arrows? This statement rings particularly true since, aside from its own few tricks (such as drawing and shooting in the same action or aiming for a bonus to hit), the archetype also gives access to a few of the fighter's archery feats (and one ranger feat) at a later level than intended.
In truth, this archetype's not really meant for fighters or rangers, who would do just as well just multiclassing to each other. Who this is meant for is everyone else who just wants to be better at shooting. If you want the fighter's feats, you're not really getting much out of multiclassing since you likely won't be needing all the proficiencies you just got and there's no crossbow support. The ranger multiclass on the other hand saddles you with an action you won't ever be able to use for combat and not as many feats for helping with combat.
|The Archetypes of Pathfinder 2nd Edition|
|Core Rule Book:||Alchemist - Barbarian - Bard - Champion - Cleric - Druid |
Fighter - Monk - Ranger - Rogue - Sorcerer - Wizard
|Lost Omens Setting Guide:||Crimson Assassin - Duelist - Guild Agent - Hellknight Armiger |
Lion Blade - Living Monolith - Magic Warrior - Runescarred - Sentry - Student of Perfection
|Adventure Path||Juggler Dedication - Staff Acrobat Archetype - Zephyr Guard Archetype|
|Advanced Player's Guide||Acrobat - Archaeologist - Archer - Assassin - Bastion - Beastmaster - Blessed One - Bounty Hunter - Cavalier - Celebrity - Dandy - Duelist - Eldritch Archer - Familiar Master - Gladiator - Herbalist - Horizon Walker - Investigator - Linguist- Loremaster - Marshal -Martial Artist - Mauler - Medic - Oracle - Pirate - Poisoner - Ritualist - Scout - Scroll Trickster - Scourger -Sentinel - Shadowdancer - Snarecrafter -Swashbuckler - Talisman Dabbler - Vigilante - Viking - Weapon Improviser -Witch|